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CALM DOWN!. -24 LKFS. Show. -24 LKFS. Show. -21 LKFS. ?. -24 LKFS. Show. -21 LKFS. Downmix Dilemma. ?. Ls. L. Lf. Surround Mix. C. Rf. R. Rs. Frequent Downmix. Producers Stereo Deliverables Networks Stereo Channels & Internet Distribution Stations

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Presentation Transcript
slide3

-24 LKFS

Show

-21 LKFS

slide4

?

-24 LKFS

Show

-21 LKFS

downmix dilemma
Downmix Dilemma

?

Ls

L

Lf

Surround Mix

C

Rf

R

Rs

frequent downmix
Frequent Downmix
  • Producers
    • Stereo Deliverables
  • Networks
    • Stereo Channels & Internet Distribution
  • Stations
    • Stereo Infrastructure & Channels
  • Consumers
    • Stereo STBs & TVs (≥61%)
downmix dilemma1
Downmix Dilemma

?

Ls

L

Lf

C

?

Surround Mix

Rf

R

Rs

?

preserve center
Preserve Center

L

0 dB

Near Field

C

Surround Mix

+6 dB

R

Average

+3 dB

preserve center1
Preserve Center

?

Ls

L

Lf

C

Surround Mix

-3 dB

Rf

R

Rs

?

preserve rear
Preserve Rear?

Ls

L

Lf

Can\'t Hear Dialog!

C

Surround Mix

-3 dB

Rf

R

Rs

adjust rear
Adjust Rear

Ls

-3 dB

L

Lf

C

Surround Mix

-3 dB

Rf

R

Rs

-3 dB

defacto standard downmix
Defacto Standard Downmix

Ls

-3 dB

L

Lf

C

Surround Mix

-3 dB

R

Rf

Rs

-3 dB

defacto compatible surround mix
Defacto-Compatible Surround Mix

C

70 dB SPL

L

C

-3 dB

70 dB SPL

R

incompatible surround mix
Incompatible Surround Mix

Power Sum

10*Log(3) = 4.8 dB

74.8 dB SPL

Lf

C

Rf

Voltage Sum

20*Log (1+.7) = 4.6 dB

Power Sum

10*Log(2) = 3 dB

77.6 dB SPL

2.8 dB Error!

L

Lf

C

-3 dB

Rf

R

bottom line
Bottom Line
  • If two ads are mixed in surround to measure -24 LKFS…
  • One can sound and measure 2.8 dB louder after downmix
  • Producers can "game" the system to be louder
  • Stations and MVPD\'s could be deemed non-complaint when broadcasting "compliant" content!
  • Not a problem when content mixed to be compatible
  • A real problem for some Public Television music shows
  • See AES e-Brief 38 for measured statistics "The Effect of Downmixing on Measured Loudness"
customize the downmix
Customize the Downmix

Power Sum

10*Log(3)

74.8 dB SPL

Lf

C

Rf

Voltage Sum

20*Log (1+.2) = 1.8 dB

Power Sum

10*Log(2) = 3 dB

74.8 dB SPL

L

Lf

C

-12 dB

Rf

R

producer controlled metadata
Producer-Controlled Metadata

Producer

Consumer

Ls

Lf

Left

C

AC3

AC3

Surround Mix

AC3 Encoder

AC3 Decoder

Right

Rf

Audio +

Metadata

Audio +

Metadata

Rs

LFE

Manual Metadata

tv station controlled metadata
TV Station-Controlled Metadata

Producers

Networks

TV Stations

Consumers

Ls

Lf

Left

C

AC3

AC3 Decoder

Surround Mix

Distribution

Plant

AC3 Encoder

Right

Rf

Audio +

Metadata

Rs

LFE

X

X

X

No Metadata Channel!

See ATSC A/85 Chapter 7

why no metadata channel
Why No Metadata Channel?
  • Many producers lack interest and ability in setting metadata
  • For a show, requires adoption by ALL distributors
  • Within a network, requires adoption by EVERY station
  • Within a station, requires adoption in ALL equipment
  • Most equipment requires obscure custom settings
  • Some equipment cannot carry metadata
  • Penalty of metadata error is severe: loss of center channel!

*

*

*I\'ll buy you a beer if you\'ll let me whine about it.

proposed solution
Proposed Solution
  • Standardize downmix for systems without metadata
    • -3 dB for Center and Rear
  • Require loudness measurement of the standard downmix
    • Encourages producers to mix appropriate to standard downmix
    • Producers can use film-style mixing or shift center channel phase
    • Penalty of an inappropriate mix is merely a show softer in surround
  • Change delivery standards
  • Modify A/85
  • Ask LKFS meter vendors to include downmix measurement
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